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Magnetron sputtering is known for its versatility, offering high quality thin film coatings for applications ranging from hard coatings to very clear optical coatings. For most of the thin film applications where magnetron sputtering is used, the thin film density is crucial factor. Either the aim is to get good refractive indexes or better protective properties, densely packed atoms in the layers are necessary. For protective coatings it is important to have layers without clear pathways along the grain boundaries from top of the layer towards the substrate. An example of the dense layers used as protective coating is given in Fig.1. The Nacos’ high quality protective coatings are dense and without prominent grain boundaries.

Figure 1 SEM images of protective coating – cross section

Higher quality coatings allow Naco Technologies to use thinner layers for protective coatings, that is especially important in case of precious metal coatings.

Not all thin film applications however require density in the layers. In fact, in some cases porous coatings are beneficial. For example, if one wants to increase the surface of a catalyst for chemical reaction. Although magnetron sputtering is associated with dense layers, it is also possible to use magnetron sputtering to create nano-structured coatings.  By changing the coater geometry – increasing the substrate to target distance and the angle of the substrate to target one can utilize GLAD – glancing angle deposition.

Besides the tilted substrate and the target – substrate distance collimation of the sputtered particles is required. To achieve collimated particle flux from the sputtering target, the deposition pressure is lowered compared to regular deposition process. Ideally the sputtering pressure is such that the mean free path – the distance that the atom have to travel before colliding with other atom in the vacuum chamber is greater than the target-substrate distance. These changes to the sputtering process change the way that the thin film grows on the substrate. In case of GLAD, the atoms stay exactly where they land on the substrate and because of self-shadowing pronounced gaps between columns appear.

Not all deposition systems will be flexible enough to undergo the changes for the sputtering process to achieve GLAD conditions. The coater used for RnD at Naco Technologies however is versatile and can be configured to achieving the necessary conditions for GLAD. SEM images of the nanostructured coatings made by Naco Technologies are shown in Fig.2.

Figure 2 SEM images of nanostructured coating - top view.

The GLAD coatings have clear columnar structure with evenly spaced columns; the diameters of the columns are roughly 50nm. There are open voids between the columns, initial measurements suggest that the surface is several orders of magnitude compared to a flat sample. The activity of the catalyst is not entirely linked to surface area, selection of the material and the purity also plays role here and has to be adjusted based on the application.

The usual benefits of magnetron sputtering is kept while utilizing GLAD - the coating is uniform across the sample, the thickness can be easily controlled, pure metals, alloys, oxide and nitride coatings can be made.

Naco can offer such coatings for any application that require increased surface and high-quality catalysts.

This research is done within the Smart Materials Competence Center (VMKC) funding structure.